Immune complexes bound to collagenous tissue in animals with antigen-induced arthritis appear to stimulate a chronic, destructive inflammation similar to rheumatoid arthritis. The phlogistic potential of these complexes will be demonstrated in in vitro assays of chemotaxis, superoxide production and lysosomal enzyme release. Elution, recovery and characterization techniques developed in the animal model will be applied to surgical specimens from patients with rheumatoid arthritis. Immunoregulatory mechanisms with suppressor cell assays have been developed and will seek to understand the cellular basis for the deposition of tissue-bound immune complexes.